This invention relates to foam molding processes and more particularly to foam molding processes in which mold release agents are provided on a mold lid to prevent the foam material from adhering thereto.
It is known to provide various forms of mold release material either on a mold lid surface or in the foam precursors to aid in the separation of a mold part from the mold lid on completion of a molding sequence.
Also various proposals are known in which molded parts have a preformed adhesive layer to permit post adhesion to another component.
The problem with wax release or foam precursor release system is that they require use of expensive release chemicals in the production process. Further, use of wax release agents can cause wax contamination of a subsequent paint process. Such contamination can result in poor adhesion of paint coatings on the foamed part.
Another problem with release systems is that the release chemicals can cause poor foam adhesion to vinyl shells contaminated by such chemicals.
U.S. Pat. No. 2,956,310 discloses a method for casting cellular resin sheets by use of cover films that are later stripped away. The strips are provided only to aid in the foaming process and are not suggested for use in a mold release system or for use in forming a post adhesive surface on a foam part.
U.S. Pat. No. 3,787,546 discloses the use of a layer of release material to provide release of a polymer composite from a mold surface. The process has the release agent contamination problem set-forth above.
U.S. Pat. No. 3,895,154 discloses a sheet of material to cover the mold cover. The sheet is coated with the silicon material and is configured to allow for escape of gas from the mold reactants. It does not provide a system for concurrently releasing a part from the mold while providing a post adhesion surface on the part.
U.S. Pat. No. 4,165,999 discloses a mold process for the manufacture of cement or gypsum products. The mold surfaces are covered by a layer of thermoplastic material which prevents water evaporation. Their is no suggestion of a system which eliminates the use of release agents in a foam molding process while providing for post adhesion of the foam part to another part.
Proposals for providing a separate adhesive layer on a various parts some including foam parts are shown in U.S. Pat. Nos. 4,590,112; 4,204,017; 3,533,899. Such adhesive layers are not formed as part of a mold release process used for the manufacture of foam parts.